Bush bearing

ABSTRACT

A bush bearing ( 1 ) is a wrapped bush bearing which has a cylindrical inner peripheral surface ( 2 ) serving as a sliding surface as well as an outer peripheral surface ( 3 ), and whose abutting faces ( 4 ) are abutted against each other. The outer peripheral surface ( 3 ) includes a cylindrical surface ( 11 ); a tapered surface ( 13 ) interposed between the cylindrical surface ( 11 ) and one annular end face ( 12 ) in an axial direction X and formed by roll forming; a smooth circular arc surface ( 14 ) interposed between the tapered surface ( 13 ) and the cylindrical surface ( 11 ); and a smooth circular arc surface ( 15 ) interposed between the tapered surface ( 13 ) and the end face ( 12 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a continuation of U.S. application Ser. No.10/580,609 filed May 25, 2006, which is a U.S. National Stage of PCTApplication No. PCT/JP2003/15017, filed Nov. 25, 2003, the contents ofall which are herein incorporated by reference.

TECHNICAL FIELD

The present invention relates to a bush bearing for rotatably supportinga shaft, and more particularly to a bush bearing which is secured at itsouter peripheral surface to a housing, for rotatably supporting at itsinner peripheral surface a shaft.

BACKGROUND ART

A bush bearing as a sliding bearing has advantages in that, as comparedwith a rolling bearing, the bush bearing is low-priced, and the amountof noise generated is low, so that it excels in the low noisecharacteristic. Because of such advantages, the bush bearings are usedin numerous fields including compressors of automobiles and the like.

The bush bearing is normally press fitted in a hole of a housing, issecured at its outer peripheral surface to the housing, and is adaptedto rotatably support at its inner peripheral surface a shaft. Tofacilitate the press fitting into the housing hole, a tapered surface isformed at an outer peripheral surface on the end face side of the bushbearing.

Incidentally, if a cutting tool (single point tool) is merely abuttedagainst the outer peripheral surface on the end face side of the bushbearing to shave it off so as to form such a tapered surface, there is apossibility that very small burrs are produced on that outer peripheralsurface. At the time of the press fitting of the bush bearing into thehousing hole, these burrs can fall off and remain in the housing hole asdust (e.g., metal powder dust). This dust can enter between the innerperipheral surface of the bush bearing and the shaft, making itimpossible to ensure smooth rotation of the shaft. In addition,particularly in an aluminum-made housing, there is a possibility thatthe inner peripheral surface of the housing defining the hole is shavedby the burrs at the time of the press fitting of the bush bearing intothe housing hole, and aluminum chips are produced. These aluminum chipscan enter between the inner peripheral surface of the bush bearing andthe shaft, making it impossible to ensure smooth rotation of the shaft.

Furthermore, if the wall thickness on the end face side of the bushbearing becomes extremely small owing to the tapered surface formed, theend face side of the bush bearing becomes easily deformed in the pressfitting into the housing hole, making it impossible to assure theroundness of the inner peripheral surface of the bush bearing.Meanwhile, if the tapered surface is formed so as to enlarge the wallthickness on the end face side of the bush bearing in order to avoidthis, the positioning and fixation of the bush bearing with respect tothe housing hole prior to the press fitting into the housing hole becomedifficult; moreover, the guiding action based on the tapered surface inthe press fitting into the housing hole is practically lost, possiblycrushing the end face side of the bush bearing or unnecessarilyenlarging the diameter of the open end of the housing hole.

DISCLOSURE OF THE INVENTION

The present invention has been devised in view of the above-describedproblems, and its object is to provide a bush bearing which makes itpossible to eliminate the occurrence of dust (e.g., metal powder dust,particularly aluminum chips) at the time of the press fitting into thehousing hole, which makes it possible to easily perform the pressfitting without crushing the open end and the like of the hole to bepress fitted into, and which makes it possible to ensure the roundnessof the inner peripheral surface even after the press fitting.

The bush bearing in accordance with a first aspect of the invention is acylindrical bush bearing whose inner peripheral surface is a slidingsurface, wherein an outer peripheral surface of the bush bearing has acylindrical surface and a tapered surface interposed between thecylindrical surface and at least one annular axial end face of the bushbearing and formed by press forming, and if the wall thickness at thecylindrical surface of the bush bearing is assumed to be t, a differenceδ(=r1-r2) between a radius r1 at the cylindrical surface of the bushbearing and a radius r2 at an outer peripheral edge of the one annularend face is in a range of not less than 0.1 t and not more than 0.3 t.

According to the bush bearing in accordance with the first aspect, sincethe tapered surface is formed by press forming, no burrs are produced atthe outer peripheral surface. Therefore, at the time of the pressfitting into the housing hole, dust (e.g., metal powder dust,particularly aluminum chips) is not produced. Moreover, since thedifference δ is not less than 0.1 t, it is possible to secure an outerperipheral edge of the annular end face having a small diameter withrespect to a hole diameter of the housing. As a result, it is possibleto reliably perform the alignment with the housing hole prior to thepress fitting into the housing hole, and to ensure the guiding actionbased on the tapered surface in the press fitting into the housing hole.In addition, since the difference δ is not more than 0.3 t, it ispossible to secure the wall thickness of the annular end face to such anextent that the deformation of the end face side does not occur in thepress fitting into the housing hole. As a result, it becomes possible toassure the roundness of the inner peripheral surface even after thepress fitting.

In the bush bearing in accordance with the invention, the wall thicknesst is not particularly limited, but it is possible to cite as a preferredexample the wall thickness t of 0.5 mm to 5.0 mm, and as a morepreferred example, the wall thickness t of 1.0 mm to 3.0 mm.

As for the bush bearing in accordance with a second aspect of theinvention, in the bush bearing according to the first aspect, thetapered surface extends in an axial direction continuously from the oneannular end face, and the cylindrical surface extends continuously inthe axial direction from the tapered surface toward another axial endface of the bush bearing.

The bush bearing in accordance with the invention may be an endlesscylindrical one (a bush bearing which does not have abutting faces), butas in a third aspect thereof the bush bearing is preferably constitutedby a wrapped bush bearing in which a plate having the sliding surface onone surface is convoluted into a cylindrical shape such that the slidingsurface is positioned on an inner peripheral side.

As for the bush bearing in accordance with a fourth aspect of theinvention, in the bush bearing according to the third aspect, the plateis constituted by a multilayered plate which includes a back platecoated with copper, a porous sintered metal layer adhered integrally toa copper coating layer on one surface of the back plate, and a slidinglayer including a synthetic resin with which the porous sintered metallayer is impregnated, and which has self-lubricity and wear resistance,a portion of the sliding layer which includes the synthetic resin beingformed on one surface of the porous sintered metal layer, and thewrapped bush bearing is formed by convoluting the multilayered plateinto the cylindrical shape such that the sliding layer is positioned onthe inner peripheral side.

The thickness of the copper coating layer which covers the back plate ispreferably 1 μm to 10 μm, more preferably 3 μm to 5 μm, and such acoating layer may be formed by plating treatment of the back plate.

As a steel plate used as the back plate, it is possible to use such as acold rolled steel (SPCC: JIS G 4141) or a structural rolled steel (SS:JIS G 3101) having a plate thickness of 0.3 mm to 3.0 mm, preferably aplate thickness of 0.6 mm to 1.8 mm.

As the metal powder for forming the porous sintered metal layer, apowder of a copper alloy is used which generally passes 100 mesh sieve,such as bronze, lead bronze, or phosphor bronze which excels infrictional wear characteristics as the metal itself Depending onpurposes, however, it is also possible to use a powder of an aluminumalloy or iron, other than the copper alloy. As the form of particle ofthis metal powder, it is possible to use one which is in lump form,spherical form, or irregular form. Preferably, the thickness of thisporous sintered metal layer is generally 0.15 to 0.4 mm, particularly0.2 to 0.3 mm. Preferably, the porosity is generally not less than 10%by volume, particularly 15 to 40% by volume.

As the synthetic resin which has self-lubricity and wear resistance andserves as the sliding layer forming material, it is possible to cite aspreferred examples polytetrafluoroethylene resin,polytetrafluoroethylene resin containing a filler material such as leador polyimide resin, polyacetal resin or oil-containing polyacetal resincontaining a lubricating oil.

As for the bush bearing in accordance with a fifth aspect of theinvention, in the bush bearing according to the fourth aspect, thetapered surface is constituted by an exposed surface of the coppercoating layer.

As for the bush bearing in accordance with a sixth aspect of theinvention, in the bush bearing according to any one of the first tofifth aspects, the tapered surface extends in the axial directionbetween the cylindrical surface and the one annular end face so as to beflat or convex toward an outside.

As for the bush bearing in accordance with a seventh aspect of theinvention, in the bush bearing according to any one of the first tosixth aspects, a smooth circular arc surface is interposed between thetapered surface and the cylindrical surface. As in the bush bearing inaccordance with an eighth aspect of the invention, such a smoothcircular arc surface preferably has a radius of curvature which is notless than 0.1 mm and not more than 1.0 mm.

As for the bush bearing in accordance with a ninth aspect of theinvention, in the bush bearing according to any one of the first toeighth aspects, a smooth circular arc surface is interposed between thetapered surface and the one annular end face. As in the bush bearing inaccordance with a 10th aspect of the invention, such a smooth circulararc surface preferably has a radius of curvature which is not less than0.1 mm and not more than 0.5 mm.

As for the bush bearing in accordance with a 11th aspect of theinvention, in the bush bearing according to any one of the first to 10thaspects, an angle of intersection, θ, between the tapered surface and anaxial line is not less than 15° and not more than 25°.

The tapered surface in the invention is formed by press forming, asdescribed above, but in the press forming, the tapered surface ispreferably formed by roll forming, as in the bush bearing in accordancewith a 12th aspect of the invention.

In the invention, the outer peripheral surface of the bush bearing issufficient if it has a tapered surface interposed between thecylindrical surface and at least one annular axial end face of the bushbearing. Preferably, however, as in the bush bearing in accordance witha 13th aspect of the invention, the outer peripheral surface of the bushbearing further has, in addition to such a tapered surface, anothertapered surface interposed between the cylindrical surface and the otherannular axial end face of the bush bearing.

The other tapered surface may be formed in the same way as theaforementioned tapered surface as in the bush bearing in accordance with14th to 22nd aspects of the invention.

According to the invention, it is possible to provide a bush bearingwhich makes it possible to eliminate the occurrence of dust (e.g., metalpowder dust, particularly aluminum chips) at the time of the pressfitting into the housing hole, which makes it possible to easily performthe press fitting without crushing the open end and the like of the holeto be press fitted into, and which makes it possible to ensure theroundness of the inner peripheral surface even after the press fitting.

Hereafter, a description will be given of the present invention and themode for carrying out the invention with reference to the preferredembodiment shown in the drawings. It should be noted that the presentinvention is not limited to the embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a preferred embodiment of the invention;

FIG. 2 is a cross-sectional view of the embodiment shown in FIG. 1;

FIG. 3 is an explanatory partially enlarged cross-sectional view of theembodiment shown in FIG. 1;

FIG. 4 is a diagram explaining a manufacturing method in accordance withthe embodiment shown in FIG. 1;

FIG. 5 is a diagram explaining the manufacturing method in accordancewith the embodiment shown in FIG. 1; and

FIG. 6 is a diagram explaining an example of use in accordance with theembodiment shown in FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

In FIGS. 1 to 3, a cylindrical bush bearing 1 in accordance with thisembodiment is a wrapped bush bearing which has a cylindrical innerperipheral surface 2 serving as a sliding surface as well as an outerperipheral surface 3, and whose abutting faces 4 are abutted againsteach other.

The outer peripheral surface 3 includes a cylindrical surface 11; atapered surface 13 interposed between the cylindrical surface 11 and oneannular end face 12 in an axial direction X and formed by press forming,or roll forming in the press forming in this embodiment; a smoothcircular arc surface 14 interposed between the tapered surface 13 andthe cylindrical surface 11; a smooth circular arc surface 15 interposedbetween the tapered surface 13 and the end face 12; a tapered surface 17interposed between the cylindrical surface 11 and the other annular endface 16 in the axial direction X and formed by press forming, or rollforming in the press forming in this embodiment; a smooth circular arcsurface 18 interposed between the tapered surface 17 and the cylindricalsurface 11; and a smooth circular arc surface 19 interposed between thetapered surface 17 and the end face 16.

Since each of the tapered surface 17, the circular arc surface 18, andthe circular arc surface 19 is constructed in the same way as each ofthe tapered surface 13, the circular arc surface 14, and the circulararc surface 15, a detailed description will be given hereafter of theside of the tapered surface 13, the circular arc surface 14, and thecircular arc surface 15, and a description of the side of the taperedsurface 17, the circular arc surface 18, and the circular arc surface 19will be omitted.

The tapered surface 13, which extends between the cylindrical surface 11and the end face 12 in such a manner as to be inclined in the axialdirection X and is constituted by an exposed surface of a copper coatinglayer 31, extends in the axial direction X continuously from the endface 12 through the circular arc surface 15 so as to be flat or convextoward the outside with a radius of curvature R1. The cylindricalsurface 11 extends continuously in the axial direction X from thetapered surface 13 through the circular arc surface 14 toward the endface 16 in the axial direction X and parallel to the axial direction X.

The smooth circular arc surface 14 interposed between the taperedsurface 13 and the cylindrical surface 11 has a radius of curvature R2which is not less than 0.1 mm and not more than 1.0 mm. The smoothcircular arc surface 15 interposed between the tapered surface 13 andthe end face 12 has a radius of curvature R3 which is not less than 0.1mm and not more than 0.5 mm. An angle of intersection, θ, between thetapered surface 13 and an axial line 20 is not less than 15° and notmore than 25°.

If the wall thickness at the cylindrical surface 11 of the bush bearing1 is assumed to be t, a difference δ(=r1-r2) between a radius r1 at thecylindrical surface 11 of the bush bearing 1 and a radius r2 at an outerperipheral edge 32 of the end face 12 is in a range of not less than 0.1t and not more than 0.3 t.

The bush bearing 1 may be manufactured as follows. Namely, a pressroller 52 having a cylindrical surface 51 as well as a press roller 54having an annular recessed surface 53 of a shape complementary to theouter peripheral surface 3, such as those shown in FIGS. 4 and 5, areprepared. A belt-shaped plate 65 consisting of a multilayered plate isinserted into a space 55 formed by the cylindrical surface 51 of thepress roller 52 and the annular recessed surface 53 of the press roller54, wherein the multilayered plate includes a back plate 61 coated withcopper serving as the coating layer 31, a porous sintered metal layer 63adhered integrally to the copper coating layer 31 on one surface 62 ofthe back plate 61, and a sliding layer 64 including a synthetic resinwith which the porous sintered metal layer 63 is impregnated, and whichhas self-lubricity and wear resistance, a portion of the layer 64 beingformed on one surface of the porous sintered metal layer 63. This plate65 is subjected to roll forming by the press rollers 52 and 54 whichrotate, thereby forming on one surface 66 of the plate 65 a surfacecorresponding to the tapered surfaces 13 and 17 and the circular arcsurfaces 14, 15, 18, and 19. Subsequently, the plate 65, which consistsof such a multilayered plate and has on one surface a sliding surface 67constituted by the exposed surface of the sliding layer 64 and on theother surface the surface 66 constituted by the exposed surface of thecoating layer 31, is cut into an appropriate length to thereby form theplate 65 in the form of a strip. The strip-shaped plate 65 thus obtainedis convoluted into a cylindrical shape such that the sliding surface 67is positioned on the inner peripheral side. After this convolution, thethus convoluted plate 65 is subjected to upsetting, as required, toarrange the cylindrical shape, thereby obtaining the wrapped bushbearing 1 shown in FIGS. 1 to 3.

According to the bush bearing 1, since the tapered surface 13 is formedby roll forming, no burrs are produced at the outer peripheral surface3. As a result, for example, at the time of press fitting into a hole 72of an aluminum-made housing 71 of a compressor of an automobile, such asthe one shown in FIG. 6, copper powder dust of the coating layer 31 dueto burrs is not produced. Further, since an inner peripheral surface 73of the housing 71 defining the hole 72 is not shaved by the burrs,aluminum chips are not produced. Moreover, since the difference δ is notless than 0.1 t, it is possible to secure the outer peripheral edge 32of the annular end face 12 having a small diameter (=2·r2) with respectto a hole diameter r3 of the housing 71. As a result, it is possible toreliably perform the alignment with the hole 72 of the housing 71 priorto the press fitting into the hole 72 of the housing 71, and to ensurethe guiding action based on the tapered surface 13 in the press fittinginto the hole 72 of the housing 71. In addition, since the difference δis not more than 0.3 t, it is possible to secure the wall thickness(radial width) of the end face 12 to such an extent that the deformationof the end face 12 side does not occur in the press fitting into thehole 72 of the housing 71. As a result, it becomes possible to assurethe roundness of the inner peripheral surface 2 even after the pressfitting with an interference.

1. A cylindrical bush bearing comprising, an inner peripheral surfacehaving a sliding surface, an outer peripheral surface having acylindrical surface, one annular axial end face, and a tapered surfaceinterposed between the cylindrical surface and at least said one annularaxial end face, a difference γ(=r1-r2) between a radius r1 at thecylindrical surface and a radius r2 at an outer peripheral edge of theone annular end face is in a range of not less than 0.1 t and not morethan 0.3 t, where t is a wall thickness of the bush bearing at thecylindrical surface of the outer peripheral surface, the bush bearingincluding a multilayered plate which has the sliding surface on onesurface thereof and is convoluted into a cylindrical shape such that thesliding surface is positioned on an inner peripheral side, saidmultilayered plate including a back plate entirely coated with copper, aporous sintered metal layer adhered integrally to a copper coating layeron one surface of the back plate, and a sliding layer including asynthetic resin with which the porous sintered metal layer isimpregnated, and which has self-lubricity and wear resistance, thecylindrical surface, the tapered surface, and the one annular end faceconsisting of an exposed surface of the copper coating layer, said bushbearing further comprising a first smooth circular arc surfaceinterposed between the tapered surface and the cylindrical surface, thefirst smooth circular arc surface having a radius of curvature which isnot less than 0.1 mm and not more than 1.0 mm, and a second smoothcircular arc surface interposed between the tapered surface and the oneannular axial end face, the second smooth circular arc surface having aradius of curvature which is not less than 0.1 mm and not more than 0.5mm.
 2. The bush bearing according to claim 1, wherein the taperedsurface extends in an axial direction continuously from the one annularend face, and the cylindrical surface extends continuously in the axialdirection from the tapered surface toward another axial end face of thebush bearing.
 3. The bush bearing according to claim 1, wherein the bushbearing is constituted by a wrapped bush bearing.
 4. The bush bearingaccording to claim 1, wherein the tapered surface extends in the axialdirection between the cylindrical surface and the one annular end faceso as to be flat or convex toward an outside.
 5. The bush bearingaccording to claim 1, wherein an angle θ of intersection between thetapered surface and an axial line is not less than 15° and not more than25°.
 6. The bush bearing according to claim 1, wherein the taperedsurface is formed by roll forming.
 7. The bush bearing according toclaim 1, wherein the outer peripheral surface of the bush bearingfurther has another tapered surface interposed between the cylindricalsurface and the other annular axial end face of the bush bearing andformed by press forming.
 8. The bush bearing according to claim 7,wherein the other tapered surface extends in the axial directioncontinuously from the other annular end face, and the cylindricalsurface extends continuously in the axial direction from the othertapered surface toward the one axial end face of the bush bearing. 9.The bush bearing according to claim 7, wherein the other tapered surfaceextends in the axial direction between the cylindrical surface and theother annular end face so as to be flat or convex toward the outside.10. The bush bearing according to claim 7, wherein a smooth circular arcsurface is interposed between the other tapered surface and thecylindrical surface.
 11. The bush bearing according to claim 10, whereinthe smooth circular arc surface interposed between the other taperedsurface and the cylindrical surface has a radius of curvature which isnot less than 0.1 mm and not more than 1.0 mm.
 12. The bush bearingaccording to claim 7, wherein a smooth circular arc surface isinterposed between the other tapered surface and the other annular endface.
 13. The bush bearing according to claim 12, wherein the smoothcircular arc surface interposed between the other tapered surface andthe other annular end face has a radius of curvature which is not lessthan 0.1 mm and not more than 0.5 mm.
 14. The bush bearing according toclaim 7, wherein an angle of intersection, θ, between the other taperedsurface and the axial line is not less than 15° and not more than 25°.15. The bush bearing according to claim 7, wherein the other taperedsurface is formed by roll forming.
 16. The bush bearing according toclaim 7, wherein the other tapered surface is constituted by an exposedsurface of the copper coating layer.